Separation of sterols from deodorizer sludges



SEPARATIGN @ld STERULS FROM DEGDQRKZ'ER SLUDGE Winters: Brown and Herbert W. iiawliugs, Rochester, N. 23., assignors to Eastman Kodak Company, Rushes tor, N. i l, a corporation of New Jersey No Drawing. Application August 25, 1957 .derial No. 680,652

12 Claims. (Ci. 26il 397l5) This invention concerns a process for separating ster- 01s, and more particularly, to a process for separating sterols from deodorizer sludges.

Sterols are desired materials of commerce as they are used in the preparation of such medicinals as cortisone and sex hormones, as Well as for starting materials in the syntheses of other products. Deodorizer sludges and other concentrates of unsaponifiable materials resulting as byproducts in the processing of fats and oils are the common sources of sterol materials. The usual method for recovering sterol materials from such fatty materials containing substantial amounts of sterol materials is to dissolve the fatty material in a solvent such as acetone or methyl ethyl ketone and to cool the resulting mixture to about 20 C. to winter out the sterol materials. However, the sterol products resulting from such wintering processes are of low purity, as substantial amounts of such oleaginous material as glycerides, fatty acids and tocopherols are also precipitated therewith. Additionally, such wintered products are mixtures of sterols and sterol esters. Hence, such wintered products must be subjected to further processing and crystallization or purification to prepare a desirable sterol product.

Several methods for separating sterols from such materials as deodorizer sludges have been proposed. However, such methods commonly are comprised of numerous and often times costly or time consuming process steps, produce mixtures of sterols and sterol esters, are low yielding or produce low purity sterols.

It would thus be desirable to have an improved process suitable for separating sterols from concentrates of sterol materials in high purity and in high yields with a minimum of process steps.

It is accordingly an object of this invention to provide a new and improved method for preparing sterols.

it is another obiect of the invention to provide a process for separating sterols from concentrates of sterol materials in high purity and in high yields with a minimum of process steps.

it is another object of this invention to provide a novel combination of process steps particularly adapted for separating sterols from deodorizer sludges.

It is also an object of this invention to provide an improved solvent medium that is particularly suited for eihciently separating sterols from oleaginous compositions containing substantial amounts of free fatty acids.

It is likewise an object of this invention to provide a novel sterol crystallization process suitable for separating sterols of at least 90% purity in high yields with a single crystallization.

it is a further object of the invention to provide an improved sterol crystallization process requiring a minimum of refrigeration.

These and other objects of the invention are attained by crystallizing sterols from an oleaginous mixture containing a substantial amount of free fatty acids prepared by saponifying and acidulating a fatty material containing a substantial amount of sterol material, the saponifirates atent cation, acidulation and crystallization steps being, effected in methanolic media as described in detail hereinbelow.

Any fatty material containing a substantial amount of sterol material can be suitably employed in the present process. Animal and vegetable oils contain relatively low concentrations of sterols and are thus not usually employed as sources of sterols as such. However, concentrates of sterols commonly result in the processing of animal and vegetable oils which are desirable starting materials in the present process, both from the standpoint of sterol concentration and of cost. Typical of such materials are deodorizer sludges, fatty acid distillation residues, still bottoms such as tall oil still bottoms, soap stocks, and the like. The preferred starting materials in the subject process are deodorizer sludges.

Deodorizer sludges are also called hot-well scum, lighter than water scum, clabber stock, condenser oil, catch basin scum, and the like, all such materials being usable in this invention and included by the generic term deodorizer sludge. Deodorizer sludges are byproducts resulting from the deodorization of fatty oils 7 with steam. The by-product sludge is usually separated from the steam in traps, condensers or similar means of separation. Deodorizer sludges derived from such vegetable oils as soybean oil, cottonseed oil, corn oil, safiiower oil, and similar fatty oils can be suitably employed in the present process. Deodorizer sludges are mixtures of several oleaginous materials including sterols, glycerides, free fatty acids and tocopherols, as well as small amounts of miscellaneous organic and inorganic materials including soaps, polymeric fatty acids and polymeric tocopherols. The sterol component in deodorizer sludges is a mixture of unesterified or free sterols and sterol esters. Deodorizer sludges usually contain from about 510% by weight of sterols, although some deodorizer sludges contain as much as 20% or even 25% by weight of sterols.

In accordance with the present process, a fatty mate rial containing a substantial amount of sterol material, such as a deodorizer sludge, is initially subjected to saponification in methanol to split the fatty acid esters. The saponification can be effected with any of the commonly used alkaline saponifying agents such as the alkali metal hydroxides, with sodium and potassium hydroxide being more generally utilized. The saponification is typically effected by combining the alkaline saponifying agent, deodorizer sludge and methanol, and thereafter heating the resulting mixture at an elevated temperature, more usually at the reflux temperature of the methanol, to substantially completely saponify the esters.

The resulting saponified mixture is thereafter acidulated to convert the resulting soaps to free fatty acids. Substantial excesses of acid over that required to decompose the soaps are to be avoided. Typically, sufficient sulfuric acid is added to convert the soaps to free fatty acids but in amounts less than is required to convert the alkali to a bisulfate.

The acidulation of the saponified mixture results in a composition composed primarily of free fatty acids, tocopherols, unesterified or free sterols, glycerol, water, methanol, and alkaline metal salts of the neutralizing acid. This mixture forms two phases, namely, an oleaginous or organic phase containing the unesterified sterols, free fatty acids, part of the methanol and tocopherols, and an aqueous phase containing glycerol, water, part of the methanol, neutralizing acid and salts. The removal of the aqueous or glycerol-containing phase from the organic phase can be easily effected as the aqueous phase settles to the bottom of the reaction mixture and can be drawn off. The methanol remaining dissolved in the organic phase serves to repress back esterification of the sterols with the free fatty acids in this phase, The separation of the glycerol-containing phase from-the organic phase is desirably effected at elevated temperatures between about 30 C. and the reflux temperature of the methanol so that sterols do not crystallize out during this step. in practice it is convenient to effect the methanolic saponification at reflux temperatures and to succes sively effect the acidulation and phase separation steps directly on the heated saponification reaction mixture.

The separated sterol-containing fatty acid composition is dissolved in a methanol-containing solvent medium composed of 9100% by volume of methanol, 90% by volume of acetone or methyl ethyl ketone, and 0l0% by volume of water. The solvent medium is thereafter cooled, and the free sterols selectively crystallized and separated therefrom as described hereinafter. A particularly effective methanol-containing solvent medium is composed of: (1) 9-40%, and preferably 14-25%, by volume of methanol; (2) 59-90%, and preferably 70- 85%, by volume of acetone or methyl ethyl ketonc; and (3) ll0% by volume of water.

The sterol-containing fatty acid composition is dissolved in the methanol-containing solvent medium at an elevated temperature, temperatures up to the reflux temperature of the solvent medium'being suitably employed. Concentrations of 1 gram of sterol-containing fatty acid composition for each l-S cc. of solvent are more generally employed, although concentrations of 1 gram of sterolcontaining fatty acid composition for each 1-l0 cc. of solvent can be suitably employed. Thereafter, the resulting solution is cooled to selectivelycrystallize out the H sterols, particularly high yields and high purities of crystallized sterol being obtained at preferred crystallization temperatures of 020 C. Filtration is more generally employed to separate the fractionally crystallized sterols from the mother liquor, although any of the other wellknown methods of separating solids from liquids such as decanting, centrifuging, and the like, can also be utilized.

The presence of methanol in the reaction mixture during the successive process steps of the present invention is particularly important as the methanol serves to repress a back-esterification of the sterols. In the absence of methanol, a mixture of sterols and free fatty acids tends to esterify in part to produce. a mixture of sterols and sterol esters. Such mixtures of partially esterified sterols are difficult to selectively crystallize in high purity and in high yields from other oleaginous materials such as free fatty acids. and tocopherols usually in admixture therewith. However, in the present process where methanol is present during each successive step, there is substantially no back-esterification of sterols with the free fatty acids, and the sterols can be readily selectively separated from the reaction mixture in high purity and in high yields.

The invention is illustrated by the following examples which describe preferred embodiments thereof.

EXAMPLE 1 Sterols were separated by the present process from a deodorizer sludge prepared by the steam deodorization of soybean oil and which contained about 35% by weight of glycerides, about 25% by weight of free fatty acids, by weight of tocopherols, about 19.2% by weight of sterols based on an infra-red assay of a saponified sample, and about 9 .8% of miscellaneous organic and inorganic materials. A 2.5 kilogram sample of the deodorizer sludge was refluxed for one hour with 1130 cc. of methanol, 53 cc. of water and 456 grams of 50% aqueous sodium hydroxide. Thereafter the resulting soaps were split by adding 1320 grams of sulfuric acid to the reaction mixture and by heating at a temperature just be low the reflux temperature of the mixture until an oil layer containing the sterols, fatty acids and tocopherols formed on top of an aqueous layer in the reaction mixture. Approximately 3 gallons of hot water (about 70 C.) were than added and the aqueous or glycerol-containing layer was drawn oil? and discarded. The remaining oil layer, or sterol-containing fatty acid composition, was washed once again with 2 gallons of hot water and phase separated as before. The fatty acid composition was then dissolved by refluxing in a solvent medium composed of 5800 cc. of acetone, 114-0 cc. of methyl alcohol and 150 cc. of water. The resulting solution was cooled to 4 C. and left at that temperature for 16 hours and thereafter filtered through a Buchner funnel. The filter cake was then washed with 500 cc. of the crystallizing solvent medium at 4 o. The Washed filter cake was then vacuum dried at about C. to yield 495 grams of material assaying 92.5% by weight of sterols by infra-red assay for a yield of 95.3%.

EXAMPLE 2 (A) In accordance with the method described in Example l, a sterol-containing fatty acid composition was prepared by saponifying and acidulating a deodorizer sludge of the type described in Example 1. Several samples of the resulting sterol-containing fatty acid composition were thereafter dissolved in various solvent media of the present invention at concentrations of 3 cc. of solvent per gram of sterol-containing fatty acid composition, crystallized and separated from the solvents by the methods described in Example 1. Table 1 below summarizes the results of these crystallizations. The proportions of solvents in Table l are expressed in terms of percent by volume.

Table 1 Crystal- Purity Yield By Solvent Medium lization Bylnfra- Infra-red,

Temperred, perpercent aturc,0. cent (a) methanol 4 01.5 02. 7 (b) methanol+5% water l 4 91. 5 K (c) 77% acetone-H075 methanol-{4% water 4 06. 0 87. 8 (d) 77% methyl ethyl ketone+19% methanol+4% water l. 4 97.5 (e) methanol 20 8.9. 5 84.0 (f) 95% methanol+5% water. 2'0 94. 5 75. 5 ((1) 77% acetone+l9% methanol-{4% w er 20 193.0 14 5 (ll) 77% methyl ethyl l methanol-H67 wate 20 99. 0 0 (i) 74% acetone+18.5%

7.5 0 water 20 98-. 0 l7. 2

(B) For comparison purposes, several samples of sterol--containing fatty acid composition prepared by saponifying and acidulating a deodorizer sludge of the type described'in Example 1 were crystallized from several solvents not of the type employed in the present invention. The samples were dissolved in the various solvent media at concentrations of 3 cc. of solvent per gram of sample, crystallized and separated from the solvents by the methods described in Example 1. Table 2 below summarizes the results of these crystallizations. The proportions of solvents in Table 2 are expressed in terms of percent by volume.

l No crystalllz ation.

The above examples illustrate that the present process can be employed to prepare sterols in high purity and in high yields with a minimum of process steps. The above examples also point-up the superiority of the present methanol-containing solvents in the present process as distinguished from conventional solvents. A practical operational advantage of the present process is also illustrated by the examples in that the sub-zero wintering temperatures usually used for separating sterol materials from other oleaginous materials are not needed in the subject process as sterols can be elficiently crystallized and separated at room temperatures, such as at about 20 C. Accordingly, refrigeration costs are substantially lower in the present process. Thus, the present process provides a particularly efficient method for separating sterols from fatty materials containing substantial amounts of sterols such as deodorizer sludges.

Although the invention has been described in detail with particular reference to typical embodiments, it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. The process for separating sterols from fatty materials containing a substantial amount of sterol material which comprises saponifying said fatty material in a methanolic alkaline medium, acidulating the resulting saponified mixture to convert the resulting soaps to free fatty acids and to produce a glycerol-containing phase and a sterol-containing phase, separating the glycerolcontaining phase from the reaction mixture, dissolving the remaining sterol-containing phase at an elevated temperature in a solvent medium comprised of 9100% by volume of methanol, 090% by volume of a ketone selected from the group consisting of acetone and methyl ethyl ketone, and 010% by volume of water, cooling the resulting solution to selectively crystallize sterols therefrom, and thereafter separating the said crystallized sterols from said solution.

2. The process according to claim 1 wherein the solvent medium is methanol.

3. The process according to claim 1 wherein the solvent medium is comprised of 90-100% by volume of methanol and 0-10% by volume of water.

4. The process according to claim 1 wherein the solvent medium is comprised of 59-90% by volume of a ketone selected from the group consisting of acetone and methyl ethyl ketone, 9-40% by volume of methanol, and 1-10% by volume of water.

5. In the separation of sterols from a deodorizer sludge, the process which comprises saponifying a deodorizer sludge in methanolic alkali, acidulating the resulting saponified mixture with suflicient sulfuric acid to convert the resulting soaps to free fatty acids, separating the resulting glycerol-containing phase from the resulting acidulated mixture, dissolving the remaining sterol-containing fatty acid composition at an elevated temperature in a solvent medium at a concentration of 1 gram of said fatty acid composition for each 1--5 cc. of said solvent medium, cooling the resulting solution to a temperature in the range of 0-20 C. and thereby selectively crystallizing sterols from said solvent medium, and thereafter separating the said crystallized sterols from said solvent medium, said solvent medium being comprised of 9-100% by volume of methanol, 0-90% by volume of a ketone selected from the group consisting of acetone and methyl ethyl ketone, and 0-10% by volume of water.

6. The process according to claim 5 wherein the solvent medium is methanol.

7. The process according to claim 5 wherein the solvent medium is comprised of 90-100% by volume of methanol and 0-10% by volume of water.

8. The process according to claim 5 wherein the solvent medium is comprised of -85% by volume of a ketone selected from the group consisting of acetone and methyl ethyl ketone, 14-25% by volume of methanol, and l10% by volume of water.

9. The process for recovering sterols from a fatty acid composition containing a substantial amount of sterols which comprises dissolving said fatty acid composition at an elevated temperature in a solvent medium at a concentration of 1 gram of said fatty acid composition for each 1-5 cc. of said solvent medium, cooling the resulting solution to a temperature in the range of 020 C. and thereby selectively crystallizing sterols from said solvent medium, and thereafter separating the said crystallized sterols from said solvent medium, said solvent medium being comprised of 9100% by volume of methanol, 0-90% by volume of a ketone selected from the group consisting of acetone and methyl ethyl ketone, and 0-10% by volume of water.

10. The process according to claim 9 wherein the solvent medium is methanol.

11. The process according to claim 9 wherein the solvent medium is comprised of -100% by volume of methanol and 0-10% by volume of water.

12. The process according to claim 9 wherein the solvent medium is comprised of 70-80% by volume of a ketone selected from the group consisting of acetone and methyl ethyl ketone, 14-25% by volume of methanol, and 1-10% by volume of water.

References Cited in the file of this patent UNITED STATES PATENTS 2,508,220 Buxton May 16, 1950 2,516,834 Bohm Aug. 1, 1950 2,523,794 Vogel Sept. 26, 1950 

1. THE PROCESS FOR SEPARATING STEROLS FROM FATTY MATERIALS CONTAINING A SUBSTANTIAL AMOUNT OF STEROL MATERIAL WHICH COMPRISES SAPONIFYING SAID FATTY MATERIAL IN A METHANOLIC ALKALINE MEDIUM, ACIDULATING THE RESULTING SAPONIFIED MIXTURE TO CONVERT THE RESULTING SOAPS TO FREE FATTY ACIDS AND TO PRODUCE A GLYCEROL-CONTAINING PHASE AND A STEROL-CONTAINING PHASE, SEPARATING THE GLYCEROLCONTAINING PHASE FROM THE REACTION MIXTURE, DISSOLVING THE REMAINING STEROL-CONTAINING PHASE AT AN ELEVATED TEMPERATURE IN A SOLVENT MEDUM COMPRISED OF 9-100% BY VOLUME OF METHANOL, 0-90% BY VOLUME OF A KETONE SELECTED FROM THE GROUP CONSISTING OF ACETONE AND METHYL ETHYL KETONE, AND 0-10% BY VOLUME OF WATER, COOLING THE RESULTING SOLUTION TO SELECTIVELY CRYSTALLIZE STEROLS THEREFROM, AND THEREAFTER SEPARATING THE SAID CRYSTALLIZED STEROLS FROM SAID SOLUTION. 